FR2704340A1 - Digitizer. - Google Patents

Abstract

This digitizer comprises a medium constituting a flat panel with which a stylus is in contact for inputting information, output means for viewing and outputting information according to the information input by means of the stylus, and a resistor arranged between the means. outlet and the middle constituting a flat panel, and forming a predetermined pattern. According to the invention, a glass substrate forming a flat panel (21) having a predetermined thickness is formed on the output means (24), the resistor (22) has a predetermined conductivity and is formed on the glass substrate (21 ) forming a predetermined pattern, and a thin dielectric layer (26) is formed on the pattern resistor (22). Since the voltage-dependent capacitance applied to the stylus is greatly increased, the signal-to-noise ratio and the operating characteristics are greatly improved.

Description

"Digitizer" The present invention relates to a digitizer, and in particular a

  digitizer having a dielectric layer formed by screen printing or vacuum deposition of a transparent dielectric material on a pattern

transparent resistive.

  The remarkable development of the electronics industry has been accompanied by numerous attempts to generate electrical signals from so-called electrographic devices. The performance requirements of these devices increase with advances in industrial areas such as computer graphics, computer-aided design (CAD), and computer-aided manufacturing.

computer (FAO).

  A digitizer is such an electrographic element. In general, a digitizer uses the same manual method that is used in conventional graphic drawing. Typically, the digitizer has been manufactured with a complicated structure of grid-type electrodes. If such a grid scanner provides a precise linear output signal, it is nevertheless true that its manufacturing cost is increased because of its complicated structure and is likely to be damaged during its use. Moreover, in different applications, it has been found desirable to manufacture such a digitizer from an extremely transparent synthetic material. However, conventional digitizers generally exclude a factor

  such as transparency. Some time ago,

  In view of the disadvantages mentioned above, a new digitizer has been realized and the characteristics of its constitution are described in detail in US Pat. Nos. 4,650,926 and 4,853,493. Due to the structure employed, there is a difference

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  feature between the two digitizers which consists of

  in that that described in the first patent (No.

  4,650,926) is structured such that a dielectric layer is deposited on a layer of a material having a predetermined resistance value, while

  that the digitizer described in the second patent (No.

  4,853,493) is structured in such a way that a layer

  resistive is deposited on an insulating layer.

  Figure 1 is a block diagram of the conventional digitizer based on a structure similar to that of the digitizer described above. Referring to Figure 1, in the conventional digitizer, a display device 14 is disposed in the lower part, a thin layer 13 of indium doped tin oxide (ITO, "indium tin oxide") is deposited on this layer and a transparent resistive layer 12, by

  example of ITO, forming a pattern is filed on this

  this. Next, a glass substrate 11 is formed on the upper portion of the patterned transparent resistive layer 12. In the figure, numeral 15 denotes a stylet that selects a desired character or symbol by being moved while still in contact with the glass substrate 11. The display device used 14 is generally a liquid crystal display panel or a panel

plasma display.

  In such a structure, the electrostatic capacitance between the stylet 15 and the transparent resistive layer 12 can be expressed by the relation C = t xA / d. The descriptive scheme used to explain this relationship is shown in FIG. 3. In this figure, the alphabetical reference C designates the electrostatic capacitance, t denotes the dielectric constant of the glass, A denotes the area of the transparent resistance forming a pattern, and d denotes the thickness of the glass substrate. In the tablet

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  conventional graph, the glass substrate is generally made of glass of a relatively large thickness. Therefore, since the electrostatic capacitance between the stylet 15 on the surface of the glass substrate 11 and the patterned transparent resistance 12 is relatively small, the signal-to-noise ratio is generally poor. As a result, it is difficult to choose the circuit elements necessary to form the digitizer and the operating characteristics of the digitizer are also decreased, which results in a decrease in the accuracy of the output signal of the display device. by

  compared to the input signal produced by the stylus.

  To solve the problems described above

  The purpose of the invention is to provide a digitizer having means which can increase the electrostatic capacitance between the stylet and the patterned transparent resistor, and to minimize the

electric noise of the display.

  To achieve this goal, a digitizer according to the invention comprises: a medium constituting a flat panel with which a stylus is in contact for the input of information; output means for displaying and providing information according to the information entered by means of the stylus; and a resistor disposed between the output means and the flat panel forming medium and forming a predetermined pattern, and is characterized in that a flat glass substrate having a predetermined thickness is formed on the output means, a resistor having a predetermined conductivity is formed on the glass substrate by forming a predetermined pattern, and a

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  Thin dielectric layer is formed on the resistor

forming a pattern.

  As described above, since the tablet to be digitized according to the invention has the thin dielectric layer formed on the transparent resistance forming a pattern, the value of the electrostatic capacitance dependent on the voltage applied to the stylet is extremely high compared to conventional digitizer, which allows the signal-to-noise ratio to be greatly increased, which will contribute to increase the quality of the products to which the invention will be incorporated, because of the improvement of their

  operating characteristics.

  The goals described above and other advantages of the invention will become more apparent to the

  reading the detailed description of a mode of

  preferred embodiment thereof given below in connection with the accompanying drawings, in which: - Figure 1 is a cross-sectional view schematically showing the structure of a conventional numeraire; - Figure 2 is a cross-sectional view schematically showing the structure of the digitizer according to the invention; and - Figure 3 is a diagram used to explain the formula giving the electrostatic capacitance. Referring to Fig. 2, a flat panel display device 24 having a predetermined thickness and size is placed in the lowest position, and a glass substrate forming a flat panel 21 also having a predetermined thickness is formed on this one. A flat panel display device, i.e. a liquid crystal device or a plasma panel, is generally used as a display device 24. In addition,

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  transparent lens 22 having a predetermined conductivity is layered on the substrate 21 and forms a predetermined pattern. Indium doped tin oxide (ITO) can be used for transparent resistance. After a dielectric paste having a predetermined dielectric constant has been repeatedly screen printed repeatedly on the patterned transparent resistance, or a dielectric layer of silicon dioxide SiO 2 or the like has been deposited under vacuum, a thin dielectric layer 26 having a thickness of about 1 to 20 μm is finally formed by a method with heating at a temperature of about 500 to 650 C. In the figure, reference numeral 25 designates a stylet which receives

  predetermined information as an input signal.

  The operation of the digitizer according to the invention constituted as indicated above is

briefly described below.

  The stylet 25 is brought into contact with the surface of the dielectric layer 26, an alternating supply voltage being applied to the stylet 25. Next, the stylet 25 is moved to be brought to the desired position of the surface of the dielectric layer 26 and an electrostatic capacitance of predetermined value is created between the tip of the stylet 25 and the lower surface of the dielectric layer 26. A voltage proportional to the electrostatic capacitance is applied to the transparent resistance forming a pattern 22. At this time, the current flowing in the transparent resistor 22 is detected by the driving circuit (not shown) in the display device 24. The current thus detected is converted into a voltage proportional to the corresponding resistance and then to a direct current by a rectifier (no represent). After that, the DC current is converted into a digital signal

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  by an analog / digital converter (CAN) (not shown) and the coordinates of a point are thus identified and the signal is displayed on the display panel of the display device 24. In such an operation, the upper dielectric layer 26, to which the electrostatic capacitance is applied by the voltage applied to the stylet 25, is of great importance. In other words, as can be seen from the relation mentioned above with the electrostatic capacitance (C = e xA / d), since the capacitance C is in inverse ratio to the thickness of the dielectric material, the higher the thickness of it is small, the greater the capacity. As the capacitance becomes high, the voltage from which a better output signal is obtained is generated while the attenuation of the voltage is reduced to a minimum. Therefore, the amplitude of the output signal is larger. To account for this relationship, a thin dielectric layer 26 having a thickness of about 1 to 20 m is disposed on the

top of the tablet.

  With respect to the etching of the display device 24, the voltage applied thereto also acts as a source of noise against the effect of which the invention uses a glass substrate 21 disposed between the display device 24 and the transparent resistor 22 to reduce noise to a minimum. As described above, since the digitizer according to the invention comprises a thin dielectric layer formed on a transparent resistance forming a pattern, the value of the electrostatic capacitance dependent on the voltage applied to the stylet becomes extremely large compared to the conventional digitizer , which allows the signal-to-noise ratio to be greatly increased, which, at its

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  turn, will contribute to improving the quality of products to which the numeral according to the invention will be incorporated, through the improvement of their operating characteristics.

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Claims (2)

  1 - Digitizer, comprising: - a medium constituting a flat panel (26) with which a stylet (25) is in contact to enter information; output means (24) for displaying and outputting information according to the information entered by means of said stylus; and a resistor disposed between the output means (24) and the flat panel forming medium, and forming a predetermined pattern, characterized in that a glass substrate having a predetermined thickness is formed on the output means (24) , the resistor (22) has a predetermined conductivity, is formed on the glass substrate (21) and forms a predetermined pattern, and a thin dielectric layer (26) is formed on the resistance forming a pattern (22).   2 - Digitizer according to claim 1, characterized in that the dielectric layer (26) is   formed with a thickness of about 1 to 20 μm.